Rodent Control

Rodent control on farms and around livestock facilities should be a multi-pronged approach as there is no exact method that is 100 percent effective. Due to the make-up of farms and the availability of feed and materials, farm sites are high-risk areas for rodent populations. A solid rodent control plan includes the use of physical and biological methods to remove rodent populations. Physical methods, such as traps are an effective and humane way of getting rid of small populations of rodents either inside or around the perimeter of the barn. There are different types of traps that can be used for pest control. Snap traps or break-back traps are very common rodent control methods. The most effective way to lure rats or mice into these traps is to use food and leave the trap alone near a wall or door for four to five days. Glue boards are also very effective and are used in a similar way as the trap. However, the use can be severely decreased by dust being captured on the glue and not allowing the rodent to be trapped. This method also can be seen as inhumane by different groups. Sound devices, usually ultrasonic, are effective in causing rodents to leave the premises without catching them. Physical methods are best when used to help control a rodent population and to deter infestation, however, many times the effectiveness of these methods are debatable and depend on the creativity of the user.

A second method to control rodents and the best method to use when dealing with an infestation is the use of rodenticides. Rodenticides are basically pesticides used to kill rodents, these products must be proven substantially effective by those that sell/produce them and the efficacy data for the products must be available to the user. There are two types of rodenticides, anticoagulants and non-anticoagulants, also known as first and second generation anticoagulants. Anticoagulants are used in 90 percent of all rodent baits with the most popular chemicals used being bordifacoum, bromadiolone and difethialone. The most used non-anticoagulants are bromethalin, cholecalciferol and zinc phosphide. It is important to know that Vitamin K1 acts as an antidote to anticoagulants. The use of rodenticides alone does not guarantee the eradication of a rodent infestation. Many times, population numbers can quickly recover if secondary methods and subsequent treatments are not applied.

First generation anticoagulants like Warfarin and Pindone are less toxic and less persistent in animal tissues. Using this type of rodenticide has a lower risk to human hazard and non-targeted animals. These products can take longer to control rat populations and surplus bait should be available for the rats to feed on. It is important to note that resistance to first generation anticoagulants is widespread in mice. Second generation anticoagulants are considerably more toxic and have a longer half-life. These products have a greater risk to non-targeted animals when ingested and require considerable less bait to be consumed by the rodents to be effective. Second generational anticoagulants are highly effective when you are dealing with a rodent infestation.

Table 2. U.S. Rodenticides Commercially Available

Compound

Classification

Trade Names

Applied Form

Warfarin

1st generation anticoagulant

Various

Meal, Water

Pindone

1st generation anticoagulant

PivalTM

PivalynTM

Meal. Water

Diphacinone

1st generation anticoagulant

RamikTM

RampageTM

TomcatTM

Blocks

Blocks

Liquid

Cholorphacinone

2nd generation anticoagulant

RozolTM

Pellets

Brodifocoum

2nd generation anticoagulant

HavocTM

JaguarTM

Blocks and Pellets

Blocks

Bromadialone

2nd generation anticoagulant

BoothillTM

HawkTM

Blocks

Meal and Blocks

Difethialone

2nd generation anticoagulant

HombreTM

Fast DrawTM

Blocks

Soft bait

Difenacoum

Non-anticoagulant CNS toxin

DiKillTM

Blocks and Pellets

Bromethalin

2nd generation anticoagulant

Cy-KilTM

RampageTM

GunslingerTM

Blocks and Pellets

Blocks

Blocks and Pellets

Cholecalciferol

Non-anticoagulant vitamin D3

Agrid3TM

Blocks and Pellets

Zinc Phosphide

Non-anticoagulant phosphine toxicity

ErazeTM

Pellets

Table adapted from Timm, 2010

The active ingredients in rodenticides vary from product-to-product and can be classified in three different ways: acute, sub-acute and chronic. Acute rodenticides are fast acting and normally are effective within 24 hours. If a non-lethal dose of acute rodenticides is consumed, rodents can have bait shyness and not consume any more of the bait. Sub-acute rodenticides cause death after several days. The lethal dose of the rodenticide may be consumed early on and feeding of this bait may continue until death. Chronic rodenticides are slow acting and cause death as early as two to three days or on average from five to seven days. Understanding what ways you will be using rodenticides, preventing, control or eradication, will help you decide what product best fits your need.

Along with the variation of active ingredients and classification of rodenticides, there are different types of bait formations. Bait products are found in the form of meals, cut or whole grain, pellets, wax blocks, edible lards/pastes/gels, contact gels or foams and gases. Particulate baits are generally more palatable to rodents when compared to wax blocks, whereas wax blocks are better in adverse conditions and areas like sewers and drainage pipes. Depending on what type of rodent you are dealing with, it may dictate what bait formation you choose. When baiting outside, like in burrows, grains are less likely to be moved or kicked out by the rodents. Care should be taken to cover baits or secure them so that the rodents are less likely to remove them.